Metal digester having a corrosion resistant metal lining



UNITED STATES PATENT OFFICE Our present invention gesters used in the those employed in the 2.022.378 METAL DIGESTER HAVING A CORROSION RESISTANT METAL LINING Paul B. Lacy, Edwin F. Libby, and Ralph V.

Covington, Va., assignors' to Metz, Industrial Chemical Sales Company, Inc., New York, N. Y., a corporation of New York No Drawing. Application Serial No.

6 Claims. relates to linings for dipulp industry particularly so-called monosulfite proc- In this process the wood or other cellulosic material is cooked with a' liquor consisting of a we have found cadmium, Monel,

bronzes to give a coating of tin, lead and various the desired properties.

Of these metals we prefer cadmium which in addition to its own properties as a protecting agent forms a layer of yellow cadmium sulfide which further acts as with the cooking liquor a protective coating.

One great advantage of the improved metal coating is that it can be applied in situ by the use of known means as for example a so-called pistol which operates. metal to be sprayed into by feeding a wire of the a flame produced by concurrent streams of a combustible gas and oxygen, the liquefied metal being atomized by a stream of air or non-oxidizing gas.

sprayed, the interior steel surface of the digester is suitably roughened with steel grit or by s the metal is sprayed in the coating has been applied, the same is preferably gone over with a to close up any porous renders the same bright ness of the coating ma preferably by scrubbing and blasting, whereupon known manner. After wire brush which tends spots on the surface and and smooth. The thicky vary from .005 to .040

Before the coating is May 9, 1935, 20,608

inch. If desired, a second coating of the same or a different metal may be sprayed over the first one.

While of particular utility for monosulfite digesters, the improved coating especially of cadmium, is also useful for ordinary acid sulfite cooks, i. e. using sodium or calcium or other sulfite salt with an excess of sulphurous acid. Accordingly, in the claims by sulfite pulp digester we intend to include those used both for monosulfite liquors and acid'sulfite liquors.

We claim:

1. A. sulfite pulp digester composed of a steel shell and having a firmly adherent, impervious, sprayed lining of a corrosion resisting metal.

2. A sulfite pulp digester composed of a steel firmly adherent, impervious, metal composed of at least ,one of the following. corrosion resisting metals: cadmium, Monel, stainless steel, tin, lead and bronze.

3. A sulfite pulp digester composed of a steel shell having a protective interior coating of sprayed cadmium.

4. A monosulfite pulp digester composed of a steel shell and having a firmly adherent, impervious, sprayed lining of a metal composed of at least one of the following corros'on resisting metals: cadmium, Monel, stainless steel, tin, lead and bronze. 3

5. A sulfite pulp digester composed of a steel shell and having a firmly adherent, impervious, sprayed lining of a corrosion resisting metal, said digester being capable of resisting the corrosive effects of the acid cooking liquors.

6. A sulfite pulp digester composed of a steel shell having a protective interior coating of sprayed cadmium of from .005 to .040 inch thick- 

